Why can't IUDs be spheres or at least something a lot less pointy? Something spherical or much more rounded and with more surface contact with the uterus could have perforations in the surface and lots of copper inside to maximize surface area.
The next problem is getting it through the cervix, but existing IUDs have to get the t-bar through the uterus. Is it so different? Couldn't there be a design that allows a IUD ball or blob to expand once inside the uterus, in a way that can be reversed to extract it, all while not presenting any remotely pointy surfaces to the uterus?
I can understand why most investment overseas (mostly for poverty-stricken areas) is focused on barrier methods like condoms (limit the spread of disease), but something like this seems worthwhile. Since the mechanism of copper IUDs is believed to be the presence of copper ions in cervical mucus [1], I'd imagine that the shape of the device isn't quite as important as its composition (correct me if I'm wrong--I haven't seen a study that the shape is important for anything more than holding it in place). If it were of a "safer" design, a woman could be more confident that the device will function without damaging her innards. As an anecdote, I know I wouldn't be comfortable with something like that in me--and I know for a fact my girlfriend isn't. (Aside: It appears they were also invented by men.)
Of note, it appears that IUDs are the most common form of birth control in China, but I seem to remember reading they were fairly common elsewhere and can't find the resource. Maybe someone else can chime in.
Edit: xxxargs (below) [2] provides some interesting information that may alleviate some of these concerns.